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Nuclear Chemistry. Chapter 25. Introduction to Nuclear Chemistry. Nuclear chemistry is the study of the structure of and the they undergo. atomic nuclei. changes. Chemical vs. Nuclear Reactions. - PowerPoint PPT Presentation

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  • NUCLEAR CHEMISTRYChapter 25

  • Introduction to Nuclear ChemistryNuclear chemistry is the study of the structure of and the they undergo.

  • Chemical vs. Nuclear Reactions

    Chemical ReactionsNuclear ReactionsOccur when bonds are brokenOccur when nuclei emit particles and/or rays

  • Chemical vs. Nuclear Reactions

    Chemical ReactionsNuclear ReactionsOccur when bonds are brokenOccur when nuclei emit particles and/or raysAtoms remain unchanged, although they may be rearrangedAtoms often converted into atoms of another element

  • Chemical vs. Nuclear Reactions

    Chemical ReactionsNuclear ReactionsOccur when bonds are brokenOccur when nuclei emit particles and/or raysAtoms remain unchanged, although they may be rearrangedAtoms often converted into atoms of another elementInvolve only valence electronsMay involve protons, neutrons, and electrons

  • Chemical vs. Nuclear Reactions

    Chemical ReactionsNuclear ReactionsOccur when bonds are brokenOccur when nuclei emit particles and/or raysAtoms remain unchanged, although they may be rearrangedAtoms often converted into atoms of another elementInvolve only valence electronsMay involve protons, neutrons, and electronsAssociated with small energy changesAssociated with large energy changes

  • Chemical vs. Nuclear Reactions

    Chemical ReactionsNuclear ReactionsOccur when bonds are brokenOccur when nuclei emit particles and/or raysAtoms remain unchanged, although they may be rearrangedAtoms often converted into atoms of another elementInvolve only valence electronsMay involve protons, neutrons, and electronsAssociated with small energy changesAssociated with large energy changesReaction rate influenced by temperature, particle size, concentration, etc.Reaction rate is not influenced by temperature, particle size, concentration, etc.

  • The Discovery of Radioactivity (1895 1898): found that invisible rays were emitted when electrons bombarded the surface of certain materials.Becquerel accidently discovered that phosphorescent salts produced spontaneous emissions that darkened photographic plates

  • The Discovery of Radioactivity (1895 1898): isolated the components ( atoms) emitting the rays process by which particles give off the penetrating rays and particles by a radioactive source

  • The Discovery of Radioactivity (1895 1898):identified 2 new elements, and on the basis of their radioactivityThese findings Daltons theory of indivisible atoms.

  • The Discovery of Radioactivity (1895 1898): atoms of the element with different numbers of isotopes of atoms with nuclei (too / neutrons) when unstable nuclei energy by emitting to attain more atomic configurations ( process)

  • Alpha radiationComposition Alpha particles, same as helium nucleiSymbol Helium nuclei, He, Charge 2+Mass (amu) 4Approximate energy 5 MeVPenetrating power low (0.05 mm body tissue)Shielding paper, clothing

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  • Beta radiationComposition Beta particles, same as an electronSymbol e-, Charge 1-Mass (amu) 1/1837 (practically 0)Approximate energy 0.05 1 MeVPenetrating power moderate (4 mm body tissue)Shielding metal foil

  • Gamma radiationComposition High-energy electromagnetic radiationSymbol Charge 0Mass (amu) 0Approximate energy 1 MeVPenetrating power high (penetrates body easily)Shielding lead, concrete

  • Review of Atomic Structure

    NucleusElectrons99.9% of the mass1/10,000 the size of the atom0.01% of the mass

  • Review of Atomic Structure

    NucleusElectrons99.9% of the mass1/10,000 the size of the atom0.01% of the massComposed of protons (p+) and neutrons (n0)Composed of electrons (e-)

  • Review of Atomic Structure

    NucleusElectrons99.9% of the mass1/10,000 the size of the atom0.01% of the massComposed of protons (p+) and neutrons (n0)Composed of electrons (e-)Positively chargedNegatively charged

  • Review of Atomic Structure

    NucleusElectrons99.9% of the mass1/10,000 the size of the atom0.01% of the massComposed of protons (p+) and neutrons (n0)Composed of electrons (e-)Positively chargedNegatively chargedStrong nuclear force (holds the nucleus together)Weak electrostatic force (because they are charged negatively

  • Chemical SymbolsA chemical symbol looks like

    To find the number of , subtract the from the

    C614

  • Nuclear StabilityIsotope is completely stable if the nucleus will spontaneously .Elements with atomic #s to are . ratio of protons:neutrons ( )Example: Carbon 12 has protons and neutrons

  • Nuclear StabilityElements with atomic #s to are . ratio of protons:neutrons (p+ : n0)Example: Mercury 200 has protons and neutrons

  • Nuclear StabilityElements with atomic #s are and .Examples: and

  • Alpha DecayAlpha decay emission of an alpha particle ( ), denoted by the symbol , because an has 2 protons and 2 neutrons, just like the He nucleus. Charge is because of the 2 .Alpha decay causes the number to decrease by and the number to decrease by . determines the element. All nuclear equations are .

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  • Alpha DecayExample 1: Write the nuclear equation for the radioactive decay of polonium 210 by alpha emission.

    Step 1: Write the element that you are starting with.Mass #Atomic #Step 2: Draw the arrow.Step 3: Write the alpha particle.Step 4: Determine the other product (ensuring everything is balanced).

  • Alpha DecayExample 2: Write the nuclear equation for the radioactive decay of radium 226 by alpha emission.

    Mass #Atomic #

  • Beta decayBeta decay emission of a beta particle ( ), a fast moving , denoted by the symbol or . has insignificant mass ( ) and the charge is because its an .

    Beta decay causes change in number and causes the number to increase by .

    0-1

  • Beta DecayExample 1: Write the nuclear equation for the radioactive decay of carbon 14 by beta emission.

    Mass #Atomic #

  • Beta DecayExample 2: Write the nuclear equation for the radioactive decay of zirconium 97 by beta decay.

    Mass #Atomic #

  • Gamma decayGamma rays high-energy radiation, denoted by the symbol . has no mass ( ) and no charge ( ). Thus, it causes change in or numbers. Gamma rays almost accompany alpha and beta radiation. However, since there is effect on mass number or atomic number, they are usually from nuclear equations.

  • Transmutation the of one atom of one element to an atom of a different element ( decay is one way that this occurs!)

  • Review420-1

    Type of Radioactive DecayParticle EmittedChange in Mass #Change in Atomic #Alpha He-4-2Beta e0+1Gamma00

  • Half-Life is the required for of a radioisotopes nuclei to decay into its products.For any radioisotope,

    # of lives% Remaining0100%150%225%312.5%46.25%53.125%61.5625%

  • Half-Life

  • Half-LifeFor example, suppose you have 10.0 grams of strontium 90, which has a half life of 29 years. How much will be remaining after x number of years? You can use a table:

    # of livesTime (Years)Amount Remaining (g)001012952582.53871.2541160.625

  • Half-LifeOr an equation!

  • Half-LifeExample 1: If gallium 68 has a half-life of 68.3 minutes, how much of a 160.0 mg sample is left after 1 half life? ________ 2 half lives? __________ 3 half lives? __________

  • Half-LifeExample 2: Cobalt 60, with a half-life of 5 years, is used in cancer radiation treatments. If a hospital purchases a supply of 30.0 g, how much would be left after 15 years? ______________

  • Half-LifeExample 3: Iron-59 is used in medicine to diagnose blood circulation disorders. The half-life of iron-59 is 44.5 days. How much of a 2.000 mg sample will remain after 133.5 days? ______________

  • Half-LifeExample 4: The half-life of polonium-218 is 3.0 minutes. If you start with 20.0 g, how long will it take before only 1.25 g remains? ______________

  • Half-LifeExample 5: A sample initially contains 150.0 mg of radon-222. After 11.4 days, the sample contains 18.75 mg of radon-222. Calculate the half-life.

  • Nuclear ReactionsCharacteristics:Isotopes o